# CVE-2026-40323: SP1 V6 Recursion Circuit Row-Count Binding Gap

> A malicious prover can bypass verification in the SP1 ZK virtual machine by constructing invalid recursive proofs, compromising proof integrity.

- **Severity:** High 8.9 (`CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:H/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Apr 2026
- **Updated:** 20 Apr 2026
- **Also known as:** GHSA-63x8-x938-vx33

## What is CVE-2026-40323?

CVE-2026-40323 is a high-severity vulnerability in succinctlabs sp1, published on 17 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

SP1 is a zero‑knowledge virtual machine that proves the correct execution of programs compiled for the RISC-V architecture. In versions 6.0.0 through 6.0.2, a soundness vulnerability in the SP1 V6 recursive shard verifier allows a malicious prover to construct a recursive proof from a shard proof that the native verifier would reject. Version 6.1.0 fixes the issue.

Weakness: CWE-354 (Improper Validation of Integrity Check Value), CWE-345 (Insufficient Verification of Data Authenticity)

## Which versions are affected by CVE-2026-40323?

6 open source packages ship an affected version, including sp1_prover, sp1_recursion_circuit and sp1_sdk. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `sp1_prover` | crates.io | From 6.0.0 | 6.1.0 |
| `sp1_prover` | crates.io | From 6.0.0 | 6.1.0 |
| `sp1_recursion_circuit` | crates.io | From 6.0.0 | 6.1.0 |
| `sp1_recursion_circuit` | crates.io | From 6.0.0 | 6.1.0 |
| `sp1_sdk` | crates.io | From 6.0.0 | 6.1.0 |
| `sp1_sdk` | crates.io | From 6.0.0 | 6.1.0 |

Products: Succinct Sp1.

## How do I fix CVE-2026-40323?

Upgrade sp1_prover to 6.1.0 or later.

## Is CVE-2026-40323 being exploited?

There is no known exploitation of CVE-2026-40323 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-40323 and fix it if it is affected.

What it is: CVE-2026-40323 is a high-severity vulnerability in succinctlabs sp1, published on 17 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-40323 in the wild and no public exploit code.

Affected packages and fixed versions:
- sp1_prover (crates.io): affected from 6.0.0; fixed in 6.1.0
- sp1_prover (crates.io): affected from 6.0.0; fixed in 6.1.0
- sp1_recursion_circuit (crates.io): affected from 6.0.0; fixed in 6.1.0
- sp1_recursion_circuit (crates.io): affected from 6.0.0; fixed in 6.1.0
- sp1_sdk (crates.io): affected from 6.0.0; fixed in 6.1.0
- sp1_sdk (crates.io): affected from 6.0.0; fixed in 6.1.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-40323/ (Markdown: https://insights.sbomify.com/CVE-2026-40323/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40323
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40323
- OSV: https://osv.dev/vulnerability/CVE-2026-40323

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-40323/
Summaries are generated and may contain mistakes; the official description above is the record.